In general, printing plate supports for lithographic printing, made of an aluminum alloy, must satisfy very stringent requirements in order to be suitable for modern printing technology. On the one hand, it must be possible to homogeneously roughen the printing plate support produced from an aluminum strip, using mechanical, chemical and electrochemical roughening methods and combinations of the described roughening methods. On the other hand, the printing plates are often subjected to a burn-in process at between 220 and 300° C. with a heating time of from 3 to 10 min after the exposure and development, in order to cure the applied photo layer. The printing plate support should lose as little strength as possible during this burn-in process, so that the printing plate supports continue to be readily handleable. The fatigue or bending cycle endurance of the printing plate supports furthermore plays a role during operation of the printing plate supports in order to be able to guarantee a long service life for the printing plate supports.
Although the previously used AlMn alloys of the type AA3003, AA3103 have a good fatigue strength compared with the likewise used printing plate supports made of an aluminum alloy of the AA1050 type, the roughening performance during the preferably used electrochemical roughening is however poor, so that an aluminum alloy of the AA1050 type is preferably used.
A further development of the aluminum alloy of the AA1050 type is known from the German laid-open specification DE 199 56 692 A1, the aluminum alloy comprising the following alloy constituents in wt. % besides aluminum:    0.3 to 0.4% Fe,    0.1 to 0.3% Mg,    0.05 to 0.25% Si,    max. 0.05% Mn,    max. 0.04% Cu.
When producing lithographic printing plate supports from an aluminum strip with the composition mentioned above, a relatively high charge carrier input is needed before achieving homogeneous roughening, in particular for the preferably employed electrochemical roughening of the aluminum strip. As a result, the roughening process is very cost-intensive. It is desirable to improve the mechanical properties of the aluminum alloy previously used to produce aluminum strips for lithographic printing plate supports. This relates in particular to the thermal stability of the printing plate supports after a burn-in process.
Recent developments are aimed at increasing the manganese content of the aluminum alloy with the iron content remaining constant, in order to achieve a higher strength after the burn-in process. A corresponding aluminum alloy is known from the International Patent Application WO 02/48415 A1. However, increased magnesium and manganese values of the aluminum alloy also entail problems with the electrochemical roughenability.